//递归反转数组
function reverseArr(arr){

    var arrIn = arr
    var arrOut = []

    function reverse(arrIn,arrOut){
        if(arrIn.length<1){
            return arrOut
        }else{
            arrOut.push(arrIn.pop())
            return reverse(arrIn,arrOut)
        }
    }
    return reverse(arrIn,arrOut)
}

console.log("reverseArr: ",reverseArr([1,2,3]));